1. Field of the Invention
The present invention relates to a ceramic material, a member for use in semiconductor manufacturing equipment, a sputtering target member, and a method for producing a ceramic material.
2. Description of the Related Art
In semiconductor manufacturing equipment used for dry processes, plasma coating, and so forth in semiconductor manufacturing, a high-reactivity halogen (e.g., F or Cl)-based plasma is used for etching and cleaning. Thus, members used in the semiconductor manufacturing equipment are required to have high corrosion resistance. In general, high-corrosion resistant metals, such as anodized aluminum and Hastelloy, and ceramic members are used. In particular, materials for electrostatic chucks, which support Si wafers, and heaters are required to have high corrosion resistance and low particle emission properties. Thus, high-corrosion resistant ceramic members composed of, for example, aluminum nitride, alumina, sapphire, are used. Long-term use of these materials causes them to corrode gradually, so that particles can be emitted. Thus, a higher corrosion resistant material is required. Magnesium oxide and spinel, which are magnesium compounds, are known to have high corrosion resistance against halogen-based plasma, compared with alumina-based materials. In particular, it is reported that a higher magnesium oxide content results in higher corrosion resistance (for example, PTL 1).
Furthermore, magnesium oxide is used for refractory materials, various additives, electronic components, phosphor materials, various target materials, underlying materials for superconducting thin films, tunnel barriers of magnetic tunnel junction devices (MTJ devices), protective films for color plasma displays (PDPs), and used as a raw material for crystalline magnesium oxide layers for PDPs. Thus, magnesium oxide has been attracting attention as a material having a very wide range of applications. In particular, magnesium oxide is used as a sputtering target material to produce tunnel barriers of MTJ devices using the tunneling magnetoresistive effect and protective films for dielectrics and electrodes of PDPs. In a MTJ device including a very thin insulator, which has a thickness of several nanometers, interposed between two magnetic layers, the electrical resistance of the device is different between when relative magnetization directions of the two magnetic layers are parallel to each other and when they are antiparallel to each other. The electrical resistance change phenomenon is referred to as the tunneling magnetoresistive effect. The utilization of the electrical resistance change in the magnetized state enables the device to be applied to, for example, magnetic heads of hard disks. PTLs 2 and 3, which are described below, are related to magnesium oxide.
[Patent Document 1] JP 3559426 B
[Patent Document 2] JP 2009-292688 A
[Patent Document 3] JP 2006-80116 A